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NYS COMMON CORE MATHEMATICS CURRICULUM Module 1 Unit 3- Proofs GEOMETRY
Unit 3- Congruence and Proofs
NAME ____________________________________
DATE Lesson # Page(s) Topic Homework
10/25 1 2-3 Introduction to Triangle Proofs No Homework
10/26 1 4 Intro to Proofs continued Lesson #1 HW 10/27 2 5-7 Congruence Criteria for Triangles-SAS Lesson #2 HW
10/28 3 8-9 Angles of Isosceles Triangles Lesson #3 HW 10/31 4 10-13 Congruence Criteria for Triangles-ASA/SSS Lesson #4 HW
11/1 4 Lesson 4 Continued QUIZ
11/2 5 14-17 Congruence Criteria for Triangles-SAA/HL Lesson #5 HW 11/3 6 18-21 Triangle Congruency Proofs
11/4 6 Continue Lesson 6 Lesson #6
11/7 7 22-23 Triangle Congruency Proofs II Lesson #7 11/8 8 24-26 QUIZ
Start Lesson 8 -Properties of Parallelograms
11/9 8 Finish Lesson 8 -Properties of Parallelograms
Lesson #8
11/10 9 27-28 Properties of Parallelograms II Lesson #9 11/14 10 29-32 Mid-Segment of a Triangle
11/15 10 Lesson 10 continued Lesson #10 11/16 11 33-36 Point of Concurrency Lesson #11
11/17 12 37-40 Point of Concurrency II Lesson #12
11/18 Review Ticket In 11/21 UNIT TEST
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NYS COMMON CORE MATHEMATICS CURRICULUM Module 1 Unit 3- Proofs GEOMETRY
Lesson 1: Introduction to Triangle Proofs Opening Exercise
Use your knowledge of angle and segment relationships from Unit 1, fill in the following
Property/Theorem Diagram/Key Words Statement
Definition of Right Angle
Definition of Angle Bisector
Definition of Segment Bisector
Definition of Perpendicular
Definition of Midpoint
Angles on a line
Angles at a point
Angles Sum of a Triangle
Vertical Angles
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NYS COMMON CORE MATHEMATICS CURRICULUM Module 1 Unit 3- Proofs GEOMETRY
Example 1: We are going to take this knowledge and see how we can apply it to a proof. In each of the following you are given information. You must interpret what this means by first marking the diagram and then writing it in proof form.
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Example 2:
The two most important properties about parallel lines to remember: 1.)
2.)
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NYS COMMON CORE MATHEMATICS CURRICULUM Module 1 Unit 3- Proofs GEOMETRY
Lesson 2: Congruence Criteria for Triangles—SAS
Side-Angle-Side triangle congruence criteria (SAS):
Given two triangles and so that (Side), (Angle),
(Side). Then the triangles are congruent. Consider how ABC could be mapped to A’B’C’.
Example1
In order to use SAS to prove the triangles below are congruent, draw in the missing labels:
a.) b.)
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Lesson 3: Angles of Isosceles Triangles
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NYS COMMON CORE MATHEMATICS CURRICULUM Module 1 Unit 3- Proofs GEOMETRY
What 2 Propereties to we now know about Isosceles triangles?
1.)
2.)
Once we prove triangles are congruent, we know that their corresponding parts (angles and sides) must also
be congruent. We can abbreviate this in a proof by using the reasoning of:
CPCTC (Corresponding Parts of Congruent Triangles are Congruent)
To Prove Angles or Sides Congruent:
1. Prove that the triangles are congruent
2. Use CPCTC to prove that the additional corresponding parts are congruent.
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LESSON 9: Family of Quadrilaterals
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NYS COMMON CORE MATHEMATICS CURRICULUM Module 1 Unit 3- Proofs GEOMETRY
In Unit 1 we discussed two different points of concurrency (when 3 or more lines intersect at a single point).
The two we discussed are the:
___________________ The point of concurrency of the perpendicular bisectors of a triangle.
___________________ The point of concurrency of the angle bisectors of a triangle.
Let’s find some more points of concurrency:
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LESSON 12: A closer look at points of Concurrency
Opening Exercise: Vocab Review
Match the term on the left with the definition on the right.
_____ 1) Centroid
a) The point of concurrency of the perpendicular bisectors of a triangle.
_____ 2) Mid-Segment
b) A line segment that connects the vertex of a triangle to the opposite side at a right angle.
_____ 3) Median
c) A line segment that joins the midpoints of two sides in a triangle.
_____4) Circumcenter
d) The point of concurrency in the altitudes of a triangle.
_____5) Incenter
e) The point of concurrency of the angle bisectors of a triangle.
_____ 6) Altitude
f) A line segment drawn from the vertex of a triangle to the midpoint of the opposite side.
_____7) Perpendicular Bisector
g) The point of concurrency of the medians of a triangle.
_____8) Orthocenter h) A line or segment that is perpendicular to a segment and bisects that segment.
Important Fact: A centroid splits the medians of a triangle into two smaller segments. These segments are
always in a 2:1 ratio.
Label the lengths of segments DF, GF, and EF as x, y and z respectively. Express the lengths of CF, BF and AF in
terms of x, y and z.
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